Development of the
Project 667 BDRM Delfin class, known to NATO as the
Delta IV, began on 10 September 1975. The first boat, K-51 was
commissioned into Northern fleet in December 1985. Between 1985 and
1990, seven Delta IVs were constructed by the Sevmashpredpriyatiye
Production Association in Severodvinsk.

The Delta IVs were
constructed in parallel to the
Typhoon class, in case the larger
boats proved unsuccessful. The Delta IV is a further modification of
the Delta III, with an increased diameter pressure hull and a longer
bow section. Displacement has increased by 1 200 tons and it is 12 m longer.

The Delta IV
is a strategic platform, designed to strike military and industrial
installations and naval bases. The submarine carries the RSM-54
Makeyev missile (NATO designation: SS-N-23 'Skiff'). The RSM-54 is a
three-stage liquid-propellant ballistic missile with a range of 8 300
km. The warhead consists of four to ten multiple
independently targeted re-entry vehicles (MIRVs), each rated at 100
kT. The missile uses stellar inertial guidance for a CEP of 500 m.

The
submarine can also launch the Novator (SS-N-15 'Starfish') anti-ship
missiles or Mk 40 anti-ship torpedoes. 'Starfish' is armed with a 200 kT
nuclear warhead and has a range of 45 km.

The
operational lifetime of these submarines was estimate to be 20-25
years, assuming normal maintenance schedules, but in the 1990s
everything changed. When the START-1 treaty was signed in 1991, five
Delta IIIs served in the Northern and nine in the Pacific Fleet.

Russia was
scheduled to dismantle one Yankee-class, five
Typhoon-class and 25
assorted Delta-class ballistic missile submarines by the year 2003.

By September
1999, US specialists had helped disassemble one Yankee and six
Deltas, while the Russians had destroyed another five ballistic
missile subs on their own using US equipment.

As of June
2000, the Russian Navy claimed that it operated five
Typhoon-class
submarines, seven Delta IV-class submarines, and 13
Delta III-class
submarines, which between them carry 2 272 nuclear warheads on 440
ballistic missiles. With the chronic funding shortages affecting the
Russian Navy, it is likely that many of these boats were of suspect
seaworthiness. However, the
Russian Navy reportedly believed that 12 nuclear ballistic missile
submarines was the minimum necessary force structure for national
security. It is likely that this force goal was maintained up until
2010 at least.

From 1999
the K-64 submarine was converted to a special purpose boat. All of
its missile silos were removed. After conversion in 2002 it was
renamed the BS-64. It is believed to be a mothership for mini
submarines and used for underwater intelligence gathering. After
protractile conversion it was relaunched in 2015. Between 2002 and
2014 remaining 6 Delta IV class submarines were overhauled and
upgraded with Sineva missiles.

By 2015 a
total of 6 Delta IV class ballistic missile submarines remain in
service with the Russian Navy.